This invention relates generally to clamping together two similarly sized, elongated, triangular-shaped pieces. More particularly, it relates to a system for two dimensional clamping at variable widths of a pair of elongated, triangular-shaped pieces. The resulting composite piece has two substantially parallel side faces and a predetermined thickness.
It has recently been discovered that substantial improvements in lumber yield can be gained by cutting a log first into a plurality of sector-shaped pieces, drying them, and then rejoining them into pairs through adhesively bonding such that the thin edge of one piece is approximately adjacent the thick edge of another piece, thereby forming parallelograms. The rough parallelograms are then machined into parallelograms of a maximum width having flat surfaces for further edge bonding of the pairs into wider widths. The edge bonded members can then be rip sawn to any required width and the shorter pieces of given widths can then be finger jointed together to form wide-width, long-length composite lumber products. The subject matter of this composite lumber manufacturing process is disclosed in issued U.S. Pat. No. 3,961,654, granted on June 8, 1976 and assigned to the assignee of the present invention. Additionally, another relatively new log cutting and rejoining process that rejoins smaller triangular- or sector-shaped pieces into composite members is that disclosed in issued U.S. Pat. No. 3,903,943 granted Sept. 9, 1975, also assigned to the assignee of the present invention. Both of the disclosures in these U.S. patents are incorporated by reference herein in order to provide one skilled in the art with a complete description and better understanding of the present invention.
In the aforementioned U.S. patents describing the processes of forming composite lumber products from triangular- or sector-shaped pieces, one of the steps in each process is that of adhesively bonding two substantially equally sized triangular-shaped pieces together into a composite piece having a predetermined thickness with substantially parallel side faces. When wooden pieces are being adhesively joined together, certain general procedures must be followed that will operate to form a satisfactory composite wood product. Of course, adhesively bonding wooden pieces together has been done for many years and certain well-known techniques and processes have been developed. However, there is presently no known suitable system for adhesively bonding two triangular-shaped pieces together as required in the processes disclosed in the aforementioned U.S. patents. Unlike conventional known adhesive bonding processes that require only edge pressure or face pressure, it is necessary to clamp and constrain the triangular-shaped pieces in both dimensions simultaneously because of the inclined joinder surfaces. If all of the triangular-shaped pieces to be clamped together into pairs were equally sized, it would be a relatively simple matter to design a suitable apparatus for clamping and joining together such triangular-shaped pieces. However, as disclosed in cited U.S. Pat. Nos. 3,961,654 and 3,903,943, the angles, as well as the thicknesses and widths, are variable depending primarily on the diameter of the particular log from which the pieces are cut. In addition, the width of an individual piece can vary along its length due to taper volume from the log. In the normal process, two similarly sized elongated triangular- or sector-shaped pieces will be preselected prior to clamping them together. In particular, the pieces to form a pair will have their included small angles substantially equal in size, this being necessary to result in a composite pair with the side faces being substantially parallel.
A method and apparatus is therefore necessary to clamp and bond triangular-shaped pieces together to form rough or finished composite members having a predetermined thickness at varying widths. The process and apparatus must also be capable of satisfying pressure and time requirements for good adhesive bonding practices and, in order to be commercially feasible, must be capable of operating rates compatible with other steps in the overall lumber manufacturing process. For example, these requirements may be on the order of 100 psi minimum glue line pressure for three minutes with a suitable operating rate being something on the order of fifteen pairs per minute.
With respect to the thicknesses of certain triangular-shaped pieces that will be clamped together, some selected pieces may have thicknesses of less than the ultimately desired composite thickness. With respect to those pieces having a narrower thickness, the clamping apparatus of the present invention can appropriately position each piece in relation to the other along the inclined joinder surfaces, such that the thickness of the resulting composite piece will be the predetermined thickness. Thus for clamping and adhesively bonding together two triangular-shaped pieces that may have slightly different thicknesses at varying widths, a machine system must be provided that will allow the variable thickness triangular-shaped pieces to slip along their juxtaposed faces in relation to each other to the predetermined thickness while accommodating the variable width of the pair. The machine system must then apply adequate clamping pressure for the necessary time to adequately bond the pieces together.
With respect to the operating rate at which the overall system produces bonded pairs of triangular-shaped pieces, it should be appreciated that the selected operating rate will be compatible with production requirements as well as with upstream and downstream equipment. In view of the cure times for commercially available adhesives, which might be on the order of from two to four minutes, it is apparent that a multi-opening clamping system will be required. In a multi-opening clamping system each of the individual clamping mechanisms must then be capable of providing the aforementioned requirements for adhesively bonding the individual triangular-shaped pieces.
Thus, from the foregoing, a primary object of the present invention is to provide a method and apparatus for clamping two elongated triangular-shaped pieces together to the predetermined thickness at a variable width.
Another object of this invention is to provide a clamp with uniform edge and face loading over the length of the pieces being clamped together.
Still a further object of this invention is to provide a multi-opening clamping system suitable for high production rates and for end loading and discharge.
Still a further object of this invention is to provide a clamping mechanism having sufficient face and edge clearance for loading and unloading.
Yet a further object of this invention is to provide an individual clamping mechanism that satisfies pressure and time requirements for meeting wood bonding standards.
These and other objects of the invention will become more apparent and better understood upon reading the specification to follow in conjunction with the attached drawings.